Model dry food systems and protein from meats are used as matrix on which substrates of amino compounds, aldehydes, and sodium nitrite may react for nitrosamine formation. Unhydrolyzed collagen forms no nitrosamines on warming with NaNO2 but hydrolyzed collagen yields n- nitrosopyrollidine. Nitroso-compound formation may be inhibited by ascorbic acid. Unidentified nitroso-compounds are formed in meat systems heated to dryness in the presence of NaNO2. Other nitroso- compounds are formed by heating primary amines, aldehydes, and NaNO2 on a dry matrix.